No, it's not. Using beginBackgroundTaskWithExpirationHandler allows you to execute any non-UI code you want to. Yes, there is a time limit, but I do not see that it is guaranteed to be 10 minutes in the dev docs (perhaps I missed it), and certainly there is nothing that indicates this to the user.
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Some Apps DO bleed battery when on Quick Start dock
- Thread starter samcraig
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Oh... Well, I've noticed my phone running out of memory quicker and battery draining... Since 4.0 but I guess there could be a variety of other factors too :/ I just assumed more ram being used = more processed being run in background = more battery usage.
Apple mentioned the time limit in the SDK preview press conference, and some apps specifically state how long they can run in the background for (like iSSH).
The method is also not a guarantee that the task will actually complete - the OS can decide that the task is using too many resources and kill it.
Developers may be using the method incorrectly, which could have an impact on the battery - but Apple chose that 10 minute limit to prevent any serious abuse.
This was my understanding too, the app call the for an specific time, to do local push for example, however the OS can kill it.
The state is saved to RAM. If the foreground app needs more RAM, the system will start killing off suspended apps.
Words with Friends hasn't been updated for iOS 4, which means it is terminated every time you leave the app. It's not impossible that some combination of WWF and an OS bug is causing excess resource usage, but it's very unlikely.
EDIT: MapQuest Navigation also runs indefinitely in the background. I used it to take me to the beach, and while I browsed the internet it continued using GPS in the background and gave me spoken directions. That app does kill a bunch of battery, but its also using GPS and 3G internet at the same time for positioning and maps. It's also free so I can't complain.
And yet - how it's suppose to be aside - I can isolate that App by having ZERO things in my quick launch bar and have amazing battery life vs having JUST that App and having diminished battery life.
I can't say it's 100 percent the same test.. But I can assure you no other setting are being changed. Usage is the same. Location of the iPhone itself is unchanged. And I've tested both ways 3 times (total of 6 tests).
EDIT: MapQuest Navigation also runs indefinitely in the background. I used it to take me to the beach, and while I browsed the internet it continued using GPS in the background and gave me spoken directions. That app does kill a bunch of battery, but its also using GPS and 3G internet at the same time for positioning and maps. It's also free so I can't complain.
MapQuest and Pandora both intend to run in the background, though (location and audio, respectively). These are exactly the kind of things iOS4 multitasking was designed around. It can result in unintentional use, for sure--if you get to your destination but MapQuest doesn't quite "see" that, you can leave it running in the background without realizing it.
Like I said in a previous post, the key problem here is that users don't have any visual (or other) indication that a particular app is actually running in the background and consuming resources. They all look the same in the "Recent Apps" list. Yes, there are icons for location being used (for example), but not which app is doing it, and no indication (AFAIK) for an app that is running a background task.
Took Ww/F off my multitasking dock. I was wondering why my battery was draining a little faster than usual. Ill have to keep a lookout for these sorts of things. Thanks for the heads up.
Which phone are you trying it on? I have an extra 3GS that I can dedicate to some testing (this evening).
Hm OK...Well I'll try it on the 3GS with 4.0.1 anyway just to see what happens. A 3GS might be a better thing to test it on since the battery percentage will tend to drop more noticeably.
I've noticed this as well and make a point to close everything once I finish using applications. Well, I do leave "Settings" in the quick change dock since it's the closest thing to SBSettings I have for the time being.
And where do you think that current state is saved?
RAM use the same amount of power when is empty or full of data, is always refreshing, the extra power comes when it reads or write, that is why i said when the sate is saved should not be any different
I make sure to close any NON Apple native apps at least once or twice a day just to avoid any battery problems..
OK here's what I did: Charged iPhone to 100%, rebooted, unplugged, started a pass and play WWF game, returned to home screen. Around 3 hours later, battery is still at 100%. WiFi was turned on and the phone has no cell service (since it has no SIM card). Given this, I didn't bother to see what happens if I kill WWF manually.
Of course, things might be different on an iPhone 4, or if you play an online WWF game, or with iOS 4.0, etc.
Pandora is designed to run in the background. I assume pausing it does not cause it to stop running.
Pausing it is simply a different state of playing audio, one that could be changed. If it did what you assumed, then pause would be not very useful as it would boot you out of the application.
It sounds most likely that some apps are simply mis-using some of the backgro
und APIs and causing problems.
By the way this is one of the reasons why Apple was so hesitant to do any multi-tasking. Someone above said that they had to close down slacker from the task switcher and it solved his problem. His problem was he was running slacker in the background and it was draining the battery. So everything worked as it was supposed to work. That is the problem with all this stuff, most people don't understand and they think their battery sucks or something is wrong.
Now people can see why Apple was so hesistant to do any multi-tasking and why with what they did they still limited it.
I noticed the same thing when I had my iPhone 4. Twitter app would drain my battery faster if it was in the Dock, but when I would remove it, the battery would last much longer.
I can't say that I've done any scientific tests, but that's what it seemed to do.
I can't say that I've done any scientific tests, but that's what it seemed to do.
"All things being equal", when it comes to a handheld electronic device with a color screen, speakers, a cellular radio, a gyroscope, a thermometer a magnetometer, ambient light sensors, a microphone, etc., is a difficult state to achieve in any non-lab environment. There's a reason they call it testing in the "wild".
So many little things factor into battery life/drain rate...screen brightness (auto brightness on/off? Was it a cloudy day or sunny?), cellular signal strength (if your local AT$T tower was down one day, the phone could need more juice searching for the next strongest signal). Was it a hot day? Humid? Heat effects battery life. Etc etc.